Surgical procedures for the treatment of patient tissue frequently require visual contact by the surgeon with a target area which is limited in size. In the field of microsurgery, a surgical operation is performed while the surgeon and his assistants simultaneously view the target area by way of respective binoculars optically coupled to the microscope along respective optical paths. These binoculars provide the surgeon and the observers with the same view of the targeted tissue.
During surgical procedures, the surgeon must move the microscope as needed to optimize his view of the tissue being treated. At different stages of the procedure, the surgeon will need to view the subject tissue from different observation angles. Accordingly, the microscope must be easily manipulatable during the procedure to allow the surgeon to accurately direct and focus the microscope at the particular area of interest. Such manipulations must be performed rapidly in order to minimize any delay in carrying out the surgical procedure. Furthermore, the surgical microscope must be supported on a stand or suspended from a ceiling support in a manner that allows the microscope to be manipulated into a desired position within a working space without any obstruction to the surgical procedure.
In addition, it is desirable that the microscope assembly be adaptable for use in different surgical disciplines without the need for tools to convert the microscope from one physical assembly to another. The need to reconfigure the assembly using tools requires that doctors, nurses or other technical personnel be trained. Such training is an added burden in terms of time, cost and effort to hospitals and medical centers. Therefore, a versatile surgical microscope in which the relative positions of various components can be changed and adjusted to meet the requirements of different disciplines, e.g., otolaryngology versus ophthalmology, is preferred.
One conventional surgical microscope assembly includes the following: a microscope; a housing or casing by means of which one or more observer's tube assemblies can be mounted to the assembly; an illumination module which changes the magnification of the object or target area visible through the binoculars of the microscope (and observer's tube assembly); a fiber optics cable which transmits light to the illumination module; a mechanical assembly for changing the tilt of the microscope; means for focusing the microscope; and an adjustable tilt-axis counterweight to balance the assembly. A second adjustable counterweight is provided to prevent lateral or transverse tip of the assembly of elements when one or more laterally extending accessories (e.g., an observer's tube assembly) are added or removed. The microscope assembly optionally includes a video path to allow the microsurgery to be recorded by a video camera.
All of these elements are mounted on a support arm coupled to a mounting member. The support arm is mounted to a mounting member suitably connected to a ceiling, wall or other counterweight stand, either directly or through an angle coupling. The support arm's position is swingable through a 180.degree. arc about the axis of the mounting member. Further, the means for mounting the microscope on the support arm is rotatable about a tilt axis extending through the mechanical assembly.
With each attachment or accessory which is incorporated as part of the assembly, the microscope assembly increases in weight. This increased weight impairs the surgeon's ability to maneuver the microscope easily and accurately. Thus, it is desirable to minimize the weight of the microscope assembly. In particular, it would be advantageous to provide a mechanism for counterbalancing a change in a moment developed about the tilt or tip axis which did not require the use of counterweights.